Lossy Acoustic Propagation

Attenuation of waves by spherical spreading, as described in §1.2.4 above, is not the only source of amplitude decay in a traveling wave. In air, there is always significant additional loss caused by air absorption. Air absorption varies with frequency, with high frequencies usually being more attenuated than low frequencies, as discussed in §E.22. Wave propagation in vibrating strings undergoes an analogous absorption loss, as does the propagation of nearly every other kind of wave in the physical world.